NROB60H3 Chapter Notes - Chapter 3: Extracellular Fluid, Electric Charge, Electric Potential
11 Jun 2018
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Chapter 3-The Neuronal Membrane at Rest
• Introduction
o Neuron conducts information over a distance by using electrical signals that move across axons
o Electrical charge in the cytosol of the axon is carried by electrically charged atoms (ions) instead
of free e-, thus the cytosol is far less conductive
o The axon is not well-insulated and there is salty extracellular fluid surrounding it that also
conducts electricity (the electrical charge will leak out)
o Action potential-nerve impulse that the axonal membrane conducts
o Potential is the separation of charge over a membrane; these sigals do’t diiish over a
distance because they exist at a fixed size and duration
o The number of neurons and the frequency of action potentials hold the information/electrical
impulses
o Cells that can generate and conduct action potentials (nerve and muscle cells) have an excitable
membrane
o When no impulses are being made by the membrane then the neuron is said to be at rest
o resting membrane potential-the difference in electrical charge across the membrane (the inside
become positive relative to the outside)
• The Cast of Chemicals
o Membrane potential involves the salty fluids, the membrane and the proteins that are in the
membrane
➢ Cytosol and Extracellular fluid
o Water makes up both extracellular fluid (bathes the neuron) and the cytosol
o Electrically charged atoms-ions are dissolved in water (cause the potentials)
o Water
▪ The uneven distribution of electrical charge because of the net positive charge on
hydrogen and the net negative charge on oxygen
▪ Held together by polar covalent bonds, this electric polarity allows water to be a good
solvent for charged or polar molecules
o Ions
▪ Ions- atoms with a net electrical charge
▪ The ions are held together by the attraction to the opposite charge (ionic bond)
▪ Spheres of hydration- when clouds of water surround ions and insulate the ions from
the other ions
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